As is mentioned on PHP.net today, the first beta release of the upcoming PHP 5.5.0 series of the language has been posted for testing - PHP 5.5.0 beta1. This is a development preview and is not meant for production use.

The PHP development team announces the release of the first beta of PHP 5.5.0. This release is the first to include the Zend OPCache. Please help our efforts to provide a stable PHP version and test this version carefully against several different applications, with Zend OPCache enabled and report any bug in the bug tracking system.

This beta includes the mentioned OPCache (formerly the Zend Optimizer+), the array_column function, support for non-scalar Iterator keys in foreach and titling your PHP CLI processes. There's other changes as well, so check out the NEWS for all of them. If you'd like to help out and test this release against your application, check out this post from Phil Sturgeon